The AEB mode is intended either for HDR shooting or to select the best image from a series of shots. For this purpose, each scene is shot multiple times with different exposure values (EV). Typically, the photographer is almost free to choose these values. Since mid-2017, DJI's firmware only allows EV values of ±0.7 EV, which is not sufficient for 360º panoramas when the sun is visible in the scene. RCPano avoids this restriction.
If you select an EV value of ±0.7, the image acquisition method built into the drones firmware is used. The images are taken with one command in quick sequence and are usually (depending on the wind) suitable for usage in an HDR program without any significant problems. This is why the ±0.7 button is green colored.
With RCPano's enhanced AEB you can also use other EV values up to ±3.0. In this case, RCPano calculates the most favorable exposure and ISO values, taking care not to allow the exposure to take too long to avoid blurring. The camera takes a picture with each of the calculated values.
You probably won't be able to use these images in an HDR program, unless the program has a very good algorithm for aligning the images. There is simply too much time between the shots because the camera has to be adjusted for each shot. However, you can choose from the individual images the ones that will be used for your panorama. If you shoot in RAW format (what you should do), you can use Photoshop, Gimp or any other program capable of editing RAW to edit the images so that they fit perfectly into your panorama. There are no limits to creativity.
Depending on the camera model and the number of images configured it's possible that even with an AV value of ±0.7 the slow version of shooting has to be used. The Spark is only capable of shooting three images with the builtin mode, the other devices are limited to five images.
Here are a few tips for working with advanced AEB:
- Shoot in RAW. This is the only way to bring down lights or lighten shadows in the shot you select for the panorama. With JPEG recordings, this is only possible with poor results.
- Shoot using manual mode. To measure exposure, rotate the copter so that the sun is on the right or left side of the copter. Start with ISO 100 and an exposure corresponding to the environment.
- Program (P) or time mode (TV) are possible, but only up to a maximum of ±3.0 total.
- Even in good weather conditions, shooting takes longer because the camera has to be set up each time before shooting. With five images per scene, even with optimal conditions you have to expect about 10 minutes duration for creating the panorama. This is not due to RCPano, but to the time taken to set the parameters in the Multicopter's firmware. With seven images per scene the duration is even longer. Always start with a full battery.
- After the first image is taken, the copter floats and does not receive any commands to adjust it's position. If your copter is poorly calibrated and tends to drift, either the panorama will be interrupted or it will be even harder to assemble individual shots of the scene. Only fly with well calibrated tools. Do not use a Spark.
- If the desired EV value is not realizable (even the DJI hardware has its limits), an error message is displayed. Select another EV value or readjust the exposure.
A panorama taken with this technique can be found in our examples section. From a height of 42 meters a total of 21 times three shots were taken in manual mode with an EV of ±2.0. With relatively little wind it took about 8 minutes to take the pictures with the Mavic Pro. No HDR images were assembled, but the best exposed image was used for its position. Of course the images were shot in RAW, allowing to manipulate the exposure in post production.
